Hello dear community members,
a long time ago, I purchased the KMR-1.8 st7753s SPI display for dirt cheap. Now for some passtime, I wanted to load funny cat .bmps on a sd card and have them displayed on the module using a genuine arduino uno, which I had already running for other stuff before.
The module being dirt cheap was an issue, since that meant there was no documentation available. Took me a whole evening, to realize the display data lines needed 3.3V instead of 5V. So at least I got the Display running for now.
What remains now is, how to get the sd card running. First I tried to follow this guide, but that one did not work, since it did not supply 3.3V to the display data lines. My Module has the same pins like the one used in the guide above.
To get at least the display running instead of a blank white state, another guide suggested adding a voltage divider with 3.3k going to ground and 2.2k going to the display data line. Doing that allowed me to finally use the display.
Next I did a full erase on a 16gb sd card with the sd card formatter. I then resized two cats to 160x128 and saved it as 24bit .bmp on the sd card.
I am using Arduino 1.8.12 and made sure the libraries are up to date. But whichever sketch I chose to use, it always says the sd card can't be initialized. I then tried to swap the sd card. Since I first used 5V on the sd card data lines, I then proceeded to do the same voltage divider to get it on 3.3V. I used the same wiring as used in the first guide. The example sketches used pin 10 as sd-cs, so I changed it to 4, as used in my wiring and in the guide. The display itself worked, therefore I tried to get the sd card part of the module working on its own.
I hooked up VCC->5V; GND->GND; 4->SD_CS; MOSI->11; MISO->12; SCK->13.
At some point I even swapped MISO and MOSI, in case I might have gotten it mixed up. Same problem as before.
Now a few questions:
- ~~Aren't the resistors for the voltage divider the wrong way around? To get 3V at least, shouldn't the 3.3k resistor be going to the display? Since 5V*(3.3/(3.3+2.2))=3V. I mean the way it is used in the guide and my build is 3V going to GND and 2V to the Display or am I misunderstanding? Could it be, that the sd card also needs 3.3V, but isn't as tolerant as the display to recognize 2V as a high?~~Did not properly read instructions, wiring went wrong
- Since the display is working, I reckon trying to get only the sd card to work would make troubleshooting easer? How should I proceed, trying to get it to work with the default example sketches for the sd card library?
To clarify, my exact wiring is as follows:
- LED- to GND
- LED+ to 5V with 45Ohms resistor
- SD_CS to 4
- MOSI to 11
- MISO to 12
- SCK to 13
- CS to 10
- SCL to 13
- SDA to 11
- A0/DC to 8
- Reset to 9
- VCC to 5V
- GND to GND
The sketches used were either the library examples or the code of the both guides.
In case I forgot to attach any important information, I apologize, I am still rather new to all of this..
Thank you for your patience!
Update: I wired the voltage dividers incorrectly... Gonna rewire and see how it works out.